Stretchable conductive Ni@Fe3O4@Polyester fabric strain sensor with negative resistance variation and electromagnetic interference shielding

Soft textile-based electronic devices are promising for the development of flexible strain sensors, and useful in the fields of manufacturing, smart robots, and wearable health monitoring. In this study, we fabricated a flexible, highly responsive, and electrically conductive hierarchical Ni@Fe3O4 textile strain sensor (Ni@PET-g-PAO/Fe3O4) by radiation-induced graft polymerization, in-situ formation of Fe3O4, and subsequent electroless deposition of nickel (Ni) on a polyester (PET) fabric. Compared with the previously reported strain sensors, our hierarchical strain sensor exhibited reveals a distinctive negative resistance variation and was an excellent stretchable conductor with the increase in strain. Fe3O4 acted as a joint component by improving the adhesion of the conductive Ni layer to the support and reducing the influence of the thermal deformation of the organic fiber on the sensitivity, while enhancing the magnetic properties of the Ni metal layer. This provided the multifunctional strain sensor with excellent robust performances. The strain sensor exhibited a fast and repeatable response and displayed long-term stability in the strain range of 0-40% and an operation frequency of 0.05-1 Hz. In addition, the strain sensor was used to detect and monitor finger bending, wrist twisting, and walking. Moreover, the strain sensor could be sewed into clothing to monitor human motions. In addition, the strain sensor exhibited excellent electromagnetic interference shielding efficiency and magnetic response. Therefore, this study provided a general and effective strategy to design smart wearable devices with high performances.